The present invention relates to an optical recording/reproducing device for recording/reproducing data in/from an optical disk or a magneto-optical disk utilizing a light beam and, more particularly, to access control thereof.
Generally, concentric or helical data recording tracks (to be referred to as tracks hereinafter) are formed on a disk-shaped recording medium such as an optical disk. During recording/reproduction, a laser beam is tracking-controlled so as to irradiate the tracks correctly. Tracking control is performed by moving an objective lens in an optical pickup, and is called lens tracking. The optical lens is held by a leaf spring or the like, which is capable of shifting, and is shifted by a shifting means such as a combination of a tracking coil and a magnet.
When data is to be recorded in or reproduced from a track other than the track currently being subjected to data recording/reproducing, access control is performed to move a carriage to the target track. The tracking actuator for the objective lens is not controlled during access control. Therefore, since the objective lens is freely movable, it is influenced by the accelerative force applied to the carriage during access, is shifted from its mechanical center and vibrates. This unnecessary vibration makes proper access difficult.
In order to solve this problem, an optical disk device is disclosed in Japanese Patent Disclosure (Kokai) No. 57-94940. According to the first embodiment of this disclosed invention, a current flowing through a voice coil of a carriage-moving voice coil motor is detected, and a corresponding control signal is supplied to a lens-tracking mechanism, thereby preventing lens vibration. Therefore, when the access period ends and current supply to the voice coil motor ceases, a control signal supplied to the lens-tracking mechanism is disabled. Then, the lens vibration, which could not be attenuated, remains and cannot be stopped immediately after the carriage is stopped. According to the second embodiment of the above invention, the vibration of the objective lens is detected by a strain gauge, and the output signal from the strain gauge is supplied to a lens tracking mechanism as a control signal, in order to prevent it. With the second embodiment, however, since the strain gauge is mounted on the leaf spring supporting the objective lens, the vibration characteristic of the leaf spring is affected. Therefore, the frequency characteristic of the lens-tracking control is degraded.